The present disclosure relates to a developing device and an image forming apparatus provided therewith, and in particular, to a developing device including a developing roller that feeds toner to an image carrying member and a toner feeding roller that feeds toner to the developing roller, and an image forming apparatus provided therewith.
In an electrophotographic image forming apparatus, an electrostatic latent image is formed on a peripheral surface of an image carrying member (a photosensitive drum) by irradiating the surface with light based on image information read from an original image or based on image information transmitted from an external device such as a computer, and the electrostatic latent image is developed into a toner image with toner fed from a developing device, and then, the toner image is transferred onto a sheet. The sheet that has undergone the transfer process then undergoes a fixing process, where the toner image is fixed thereon, and then the sheet is ejected to outside the apparatus.
Now, image forming apparatuses have recently come to have complicated structures to achieve high performance such as color printing and increasingly high-speed processing, and the high-speed processing requires high-speed rotation of a toner stirring member inside the developing device. Specifically, with a developing method where a two-component developer including a magnetic carrier and toner is used with a magnetic roller (a toner feeding roller) to carry the developer and a developing roller to carry only the toner, in an opposing portion where the developing roller and the magnetic roller face each other, only the toner is carried on the developing roller via a magnetic brush formed on the magnetic roller, and further, such part of the toner as has been left without being used for development is ripped off from the developing roller. This causes the toner to be prone to float around the opposing portion where the developing roller and the magnetic roller face each other, and such toner accumulates in the vicinity of an ear cutting blade (a thickness regulating member), and if the accumulated toner aggregates and adheres to the developing roller, it may lead to dropping of the toner and result in a defective image.
As a countermeasure, for example, there has been known the following developing device that uses a two-component developer including a magnetic carrier and toner, the developing device having a magnetic roller to carry the developer and a developing roller to carry only the toner. That is, an air inlet hole for taking-in air from outside the developing device is formed through a wall of a developing container, the wall facing the developing roller and the magnetic roller, to thereby generate an air flow to make toner floating around an ear cutting blade move upward.
Even in the case, however, where such an air inlet hole is provided to take in air from outside the developing device, if the apparatus itself operates at a high speed and a large amount of toner floats, it is difficult to fully put the floating toner into the air flow generated by the rotation of the magnetic and developing rollers. This may allow the toner to accumulate and aggregate around the ear cutting blade.
The present disclosure has been made to solve the problems described above, and an object of the present disclosure is to provide a developing device capable of effectively reducing accumulation and aggregation of toner around a thickness regulating member, and an image forming apparatus provided therewith.